Definitions

Question 1

hapten

Answer 1

a molecule that must combine with an endogenous protein to elicit an allergic reaction

Question 2

chemical idiosyncrasy

Answer 2

a genetically determined abnormal reactivity to a chemical (e.g., extreme sensitivity to low doses or extreme insensitivity to high doses of a chemical)

Question 3

additive effect

Answer 3

combined effect of 2 chemicals is equal to the sum of the effects of each agent given alone

e.g., 2 OP given together cause the cholinesterase inhibition to be additive

Question 4

synergistic effect

Answer 4

combined effect of 2 chemicals are much greater than the sum of the effects of each agent given alone

e.g., carbon tetrachloride and ethanol are hepatotoxic compunds, but together produce much more liver injury than the mathematicla sum of their individual effects on liver at a given dose would suggest

Question 5

potentiation

Answer 5

occurs when 1 substance dose not have a toxic effect on a certain organ or system but when added to another chemical makes that chemical much more toxic

e.g., isopropanol is not hepatotoxic unless administerd with carbon tetrachloride, which produces an effect greater than carbon tetrachloride alone

Question 6

antagonism

Answer 6

occurs when 2 chemicals administered together interfere with each other’s actions or 1 interferes with the action of the other

there are 4 types

e.g., basis of many antidotes

Question 7

functional antagonism

Answer 7

occurs when 2 chemicals counterbalance each other by producing opposite effects on the same physiological function

e.g., low blood pressure from barbiturate intoxication can be corrected by IV administration of the vasopressor agent norepinephrine or metaraminol

e.g., chemicals triggering convulsions can be controled by giving anticonvulsants like benzodiazepines (e.g., diazepam)

Question 8

chemical antagonism or inactivation

Answer 8

chemical reaction between 2 compounds that produces a less toxic product

e.g., 2,3-dimercaptosuccinic acid (DMSA; Succimer) chelates with metal ions such as arsenic, mercury, and lead and decreases toxicity

e.g., antitoxins in treatment of various animal toxins

e.g., strongly basic low-molecular-weight protein protamine sulfate to form a stable complex with heparin, which abolishes its anticoagulant activity

Question 9

dispositional antagonism

Answer 9

disposition (i.e., absorption, distribution, biotransformation, or excretion of a chemical) is altered so that the concentration and/or duration of the chemical at the target organ are diminished

e.g., prevention of absorption of toxicant with ipecac or charcoal

e.g., increased excretion of chemical from osmotic diuretic or alteration of pH or urine

e.g., using microsomal enzyme inducers (e.g., phenobarbital) to increase metabolism/biotransformation of toxicant to less toxic metabolites

e.g., inhibiting metabolism of OP insecticide parathion with SKF-525A or piperonyl butoxide to inhibit microsomal enzyme activity

Question 10

receptor antagonism (blockers)

Answer 10

occurs when 2 chemicals that bind to the same receptor produce less of an effect when given together than the addition of their separate effects or when 2 chemical antagonizes the effect of the second chemical

e.g., naloxone treats the respiratory depressive effects of morphine and other morphine-like narcotics by competitive binding to the same receptor

e.g., antiestorgen drug tamoxifen to lower breast cancer risk among women at high risk for this estrogen-related cancer by blocking estradiol from binding to its receptor

e.g., OP insecticide poisoning with atropine by blocking the cholinergic receptor for the excess acetylcholine that accumulates by poisoning of the cholinesterase by the OP